1) Field of the Invention
This invention relates generally to the fabrication of metal fuses for semiconductor devices and more particularly to the fabrication of protective moisture proof layers over a metal fuse in a semiconductor device.
2) Description of the Prior Art
Increasing metal levels for complex/powerful circuit functions are required for future semiconductor device designs. But it makes the redundancy technology of poly fuse by laser repairing become very difficult due to too many oxide cover above fuse. Replacing the poly fuses with metal fuses is the simplest approach to overall overcome this barrier. Metal fuses with laser cuts would be preferred by industry but there are problems with fuse reliability. However, the inventors have identified problems where adjacent and neighboring metal fuse are encroached or corroded by the humidity through the micro-cracking path formed during laser energy exposure. Metal corrosion is a major issue for metal fuses with the same passivation scheme. The inventor has found that metal fuses are much more sensitive to corrosion than poly fuses.
The importance of overcoming the general problem of corrosion of fuses noted above is evidenced by the extensive technological development directed to the subject, as documented by the relevant patent and technical literature. The closest and apparently more relevant technical developments in the patent literature can be gleaned by considering U.S. Pat. No. 5,538,924(Chen), U.S. Pat. No. 5,585,662(Ogawa). U.S. Pat. No. 5,365,104(Godinho, et. al.), U.S. Pat. No. 5,578,517(Yoo), U.S. Pat. No. 4,628,590(Udo), U.S. Pat. No. 4,827,325(Or-Back et al.), U.S. Pat. No. 5,585,662(Ogawa) and U.S. Pat. No. 4,413,272(Mochizuki).